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Twins fetal development - 20 weeks pregnant

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At 20 weeks hair on the scalp is sprouting and sensory development evolves rapidly. The nerve cells serving each of the senses - taste, smell, hearing, seeing, and touch - are now developing in their specialised areas of the brain. Nerve cell production slows down as existing nerve cells grow larger and make more complex connections. The smell of a newborn seems to be the most developed of all senses, enabling them to recognize you immediately.

You no doubt feel the kicking and somersaulting of your growing twins. At times, they may be so mobile that they will wake you up during the night. The next ten weeks or so will be your twins' busiest and most active time, until the uterus gets too crowded.

A whitish coat of a slick, fatty substance called vernix caseosa will begin to cover your twins. It protects their skin during its long immersion in amniotic fluid and acts as a barrier against infection after birth. Your twins are swallowing an increasing amount of amniotic fluid, good practice for their digestive systems.

Until now your fetuses have been measured from crown to rump but from 20 weeks the measurement will be from crown to heel. And from crown to heel they are approximately 10.5 inches/ 27 centimetres long. Their eyebrows and eyelids are fully developed and fingernails cover the fingertips.

Your babies can now hear your conversations. If you talk, read, or sing to your twins, sound waves are transmitted along your spine to make them progressively familiar to your voice, helping them to recognise you after they are born.

Your twins can hear other sounds through the skin covering your belly, but they are distorted as they pass through your fat and muscle, the wall of your uterus and amniotic fluid. Only your voice will be clearly recognisable to them by the end of your pregnancy.

Most mums-to-be detect their twins movements (called quickening) between 18 and 22 weeks of pregnancy. If you've been pregnant before, you'll feel things earlier rather than later. What you may first think is a rumbling stomach may be your twins doing some back flips.

Note: Experts say every baby develops differently -- even in utero. These fetal development pages are designed to give a general idea of how a fetus grows in the womb.